The present invention relates generally to spacecraft, and more particularly, to apparatus and methods that use smart materials to deform backup structures for the purpose of pointing or controlling non-deployable or deployable appendages on a spacecraft.
The assignee of the present invention manufactures and deploys communication satellites. Such communication satellites carry deployable appendages such as reflector antennas that are directed towards the Earth, and solar wings, and the like. In certain instances, the reflector antennas must be steered to point them in a different direction or to compensate for thermal distortions or spacecraft motions.
Current mechanisms that are used to point such deployable appendages, and in particular the reflector antennas, include deployment and positioning mechanisms (DAPMs), antenna positioning mechanisms (APMs), bias adjustment mechanisms (BAMs) and two-axis antenna pointing mechanisms (TAAPMs). Both the bias adjustment mechanism and antenna positioning mechanism consist of two linear actuators which rotate the reflector about a pivot. The deployment and positioning mechanism and two-axis antenna pointing mechanism are both rotary mechanisms which allow them to have more range but larger step sizes than the bias adjustment mechanisms and antenna positioning mechanisms.
It would be desirable to have apparatus and methods for pointing a non-deployable or deployable appendage, such as a reflector antenna, disposed on a satellite that improves the pointing accuracy compared to conventional antenna pointing techniques. It is therefore an objective of the present invention to provide for improved apparatus and methods that use smart materials to deform a backup structure used to secure a non-deployable or deployable appendage for the purpose of pointing the non-deployable or deployable appendage attached thereto.
To accomplish the above and other objectives, the present invention uses smart materials, such as piezoelectric elements, to deform a backup structure holding a non-deployable or deployable appendage disposed on a spacecraft. The controllable deformation provided by the smart materials is used to point or position reflector antennas, or other non-deployable deployable appendages disposed on the spacecraft.
More particularly, apparatus and methods are provided for pointing a non-deployable deployable appendage disposed on a spacecraft. The appendage is secured to a backup structure comprising a plurality of beams. A plurality of control beams are secured to the backup structure. A plurality of deformation control elements, such as piezoelectric elements, for example, are secured to selected surfaces of the plurality of control beams. The deformation control elements are connected to a control source, such as a voltage control source, for example. Selected deformation control elements are activated to deform the associated control beams to point the deployable appendage in a desired direction.
For example, a reflector backup structure is used to secure a reflector antenna to the spacecraft. One or more piezoelectric elements or patches are disposed at predetermined locations on the reflector backup structure. The reflector backup structure may have its deformation controlled by controlling the voltage applied to the piezoelectric elements in order to deform the reflector backup structure and point the reflector antenna attached thereto.
The present invention uses the reflector backup structure with its piezoelectric elements as a controllable, deformable positioning mechanism. The present invention provides for high bandwidth, high resolution positioning of a reflector antenna, or the like, with few (or no) moving parts. The reflector backup structures or other non-deployable deployable appendage may be tailored to minimize size and mass.